partner work

In history all the classes have a CIvil War Project with groups of 3. I am in a group with myself and my 2 friends in the class. For our project we have to make a powerpoint and a page essay, and the almost all the work was suppose to be done in class, but we didnt finish on time so we worked on it after school. Well only me and one of my friend worked on it, my other friend was "busy." Anyways the TWO of us finished our essay and powerpoint in one night. Then my friend that didnt help us just waltzes in and acts like she did all the work! THE NERVE!!! I was SOOO PISSED! and we have to anonymously grade out partners and im probably going to give her a 7 out of 10. But really?! we did the work so dont act like you did sHIT!! UGH!